Piston hammer for rock drills



. E. B. DAvl-:Y ETAL '2,318,063

PISTON HAMMER FOR ROCK DRILLS Filed Nov. 2e, 1941 l www I. e

Patented May 4, 1943 UNi'TED STATE.

PlSTON HAMMER FOR ROCK DRLLS Edwin B. Davey, Glendale, and Ernest N. Martinson, Riverside, Calif.

3 Claims.

This invention relates to rock drills and particularly pertains to an improved piston hammer therefor.

It has been found that in the use of rock drilling apparatus of the pneumatic type, the striking face of the piston hammer of the type in general use fails, by cupping or otherwise, after a comparatively short period of use. This necessitates discarding of the entire piston hammer regardless of the fact that but a small portion of the useful life of the major parts of the hammer was expended. The result of this has been a high maintenance cost of such equipment.

It is the principal object of the present invention to provide an improved piston hammer of a construction which enables eficient use of the piston hammer for the full life of the major parts thereof by increasing the durability of the striking face and enabling the same to be expeditiously and economically replaced in the event of its failure.

It has been found that in drilling in hard formations a piston hammer made in accordance with prior practice became unusable because of striking face failure after twenty to twenty-five drilling shifts, while a piston hammer constructed according to the present invention increases the useful life thereof to over three hundred drilling shifts. This, of course, greatly reduces the maintenance cost of the equipment and decreases time losses necessitated by replacements.

One form which the invention may assume is exemplified in the following description and illustrated by way of example in the accompanying drawing, in which:

Fig. 1 is a fragmentary View in longitudinal section through the chuck end of a pneumatic rock drill showing the improved piston hammer construction.

Fig. 2 is a view of the striking end of the piston hammer.

Fig. 3 is a perspective view of the striking face insert.

Referring more particularly to the accompanying drawing, lili indicates the chuck end of a rock drill of the pneumatic type, which includes a chuck II, a drill steel I2 and the piston hammer I4. The latter is exteriorly iluted as at l5 to properly engage the chuck II.

In our improved construction the piston hammer is turned out of steel suitable for the purpose, and its striking end I6 is counterbored as at I1 to provide a socket for receiving a replaceable striking face insert I8.

The diameter of the striking face insert is greater than the diameter of the drill steel or tappet end against which it impacts in order that the face insert absorb the entire blow.

The insert is preferably made of a high grade head-treated alloy steel of characteristics giving it maximum resistance to the destructive effects of the impacts. This material, of course, is costly and to make the entire hammer of such material Would be commercially unfeasible because of prohibitive cost.

The striking face insert I8 is comparatively long in comparison With its diameter in order to better withstand the impacts without distortion or destruction. The peripheral meeting edges of the socket and insert I8 are iilleted as at i9 to prevent cracking of the hammer body.

The fit between the striking face insert and the socket is preferably a driving fit. To aid in removing the insert for replacement, the bore 2S of the insert is formed with an interior annular shoulder 2| which enables a drift pin to be inserted into the hammer and against the shoulder 2l so that the insert I8 may be driven out of the counterbore and replaced.

By our invention we have been enabled to increase the life of the striking end of a piston hammer to a point where the entire piston hammer does not have to be replaced until its major parts have failed because of Wear o'r crystallization. By this we have not only decreased the maintenance cost of the apparatus concerned but have materially reduced time losses due to comparatively frequent piston hammer replacements.

While we have shown the preferred form of our invention, it is to be understood that various changes may be made in its construction by those skilled in the art without departing from the spirit of the invention as defined in the appended claims.

Having thus described our invention, what We claim and desire to secure by Letters Patent is:

l. A piston hammer comprising a one-piece body having an axially disposed counterbore extending inwardly from its striking end, and a striking face insert having higher wear and impact resistant qualities than the body fitting the counterbore and secured therein, said insert having a bore therethrough, an annular abutment in said bore engageable through the inner end of the insert to enable removal thereof from the counterbore.

2. A piston hammer comprising a one-piece body having an axially disposed counterbore extending inwardly from its striking end, and a striking face insert of a length greater than its diameter and of a material having higher wear and impact resistance qualities than the body fitting the counterbore and secured therein by a driving t With its outer end ush with the end face of the lbody, said insert having a bore therethrough, an annular abutment in said bore engageable through the inner end of the insert to enable removal thereof from the counterbore.

3. A piston hammer comprising a one-piece body having an axially disposed counterbore extending inwardly from its striking end, and a striking face insert having higher Wear and impact resistant qualities than the body tting the counterbore and secured therein, said insert having a bore therethrough, an annular abutment in said bore engageable through the inner end of the insert to enable removal thereof from the counterbore, the meeting annular edge between the inner face of the counterbore and its peripheral face being illeted, the corresponding edge of the insert being formed complementary thereto.

EDWIN B. DAVEY.

ERNEST N. MARTINSON. 

